int LED = 2;
int PB = 18;
void setup() {
  // put your setup code here, to run once:
pinMode(LED, OUTPUT);
digitalWrite(LED, LOW);
pinMode(PB, INPUT_PULLDOWN);
}

void loop() {
if(digitalRead(PB)==HIGH){
  digitalWrite(LED, HIGH);
}else{
  digitalWrite(LED, LOW);
  }

}